We are investigating the interactions of bisulfite with nucleic acids and other important cell components. We wish to understand the nature of the important biochemical effects that bisulfite may induce in living cells, and the exact molecular basis of these effects. A particular emphasis is placed on the genetic properties of bisulfite, which may result from direct reactions with nucleic acids. The following specific investigations will be carried out in the coming year: a) The effect of post-treatment buffer incubations, and of the pH of plating on bisulfite mutagenesis in E. coli A38 will be explored. The same studies will be conducted in E. colimutants defective in the ung gene. b) The broad comparison will be made of the rates of spontaneous and bisulfite-catalyzed deamination of 5-methyldeoxycytidine. c) The relative reactivity of single and double stranded DNA to bisulfite-NH2NH14CONH2 transamination will be determined. d) Fluorescence studies will be carried out on poly I . poly C modified by transamination with beta-naphthylamine and bisulfite.